Ensure types crates don't use alloc with CI

Update the crates to build with the `thumbv7m-none-eabi` target using
only the `core` crate from std

.github/workflows/build.yaml

@@ -244,6 +244,33 @@ jobs:
         with:
           files: lcov.info
 
+  build-no-alloc:
+    runs-on: ubuntu-20.04
+    needs:
+      - "rustfmt"
+      - "markdown-lint"
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ./.github/actions/sgxsdk
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+      - run: rustup component add rust-src --toolchain nightly-x86_64-unknown-linux-gnu
+      - uses: r7kamura/rust-problem-matchers@v1
+      - name: Build types with no alloc crate
+        # Some notes on this build command:
+        # - The vendored headers are used to get the necessary DCAP headers
+        # - The installed `tlibc` is used to get a compilable `time.h` for the target.
+        # - In the unlikely event that `thumbv7m-none-eabi` was installed with rustup, this would error out with
+        #   duplicate core symbols due to `-Z build-std=core`.
+        run: |
+          cargo metadata --no-deps --format-version=1 |  \
+            jq -r '.packages[].name' | \
+            grep -e types | \
+            xargs -n1 sh -c 'CFLAGS="-isystem${GITHUB_WORKSPACE}/core/build/headers -isystem/opt/intel/sgxsdk/include/tlibc" cargo build -Z build-std=core --target thumbv7m-none-eabi -p $0 || exit 255'
+
   notify:
     runs-on: ubuntu-latest
     if: failure() && ${{ github.event_name }} == 'push'

Cargo.toml

@@ -37,6 +37,14 @@ exclude = [
     "test_enclave",
 ]
 
+# We need to explicitly specify resolver 2.
+# We shouldn't have to per https://doc.rust-lang.org/edition-guide/rust-2021/default-cargo-resolver.html, however if you
+# remove this, `getrandom` will fail trying to find `std` when building `mc-sgx-core-types`.  This is because
+# `mc-sgx-core-types` uses `rand` in it's `dev-dependencies`.  `rand` will use the `std` feature of `getrandom`, however
+# being in `dev-dependencies` it shouldn't normally get pulled in during a build.
+# Even specifying `edition = "2021"` here will not fix this
+resolver = "2"
+
 [profile.dev]
 opt-level = 0
 lto = true

core/build/README.md

@@ -9,6 +9,30 @@
 
 Utilities for compiling FFI wrappers to SGX libraries.
 
+## Environment Variables
+
+Below are environment variables that affect the building of the SGX FFI
+wrappers.
+
+- `SGX_SDK` The path to the Intel SGX SDK. Provides:
+
+  1. The location of the SGX SDK headers.
+
+     Note: the DCAP headers are assumed to be in the default system include path
+  2. The location of the SGX SDK libraries for linking
+
+  When `SGX_SDK` is not set:
+
+  1. The vendored local directory `headers/` will be used for compile time
+     includes
+  2. `/opt/intel/sgxsdk` will be used as the linking directory for SGX SDK
+     libraries
+
+- `CFLAGS` - Used when generating the rust bindings. Useful to specify
+  system include paths. Multiple arguments can be separated with whitespace.
+  This does **not** support escaped whitespace as specified in
+  <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html>
+
 [crate-image]: https://img.shields.io/crates/v/mc-sgx-core-build.svg?style=flat-square
 [crate-link]: https://crates.io/crates/mc-sgx-core-build
 [license-image]: https://img.shields.io/crates/l/mc-sgx-core-build?style=flat-square

core/build/src/lib.rs

@@ -69,13 +69,33 @@ pub fn sgx_builder() -> Builder {
         .ctypes_prefix("core::ffi")
         .allowlist_recursively(false)
         .parse_callbacks(Box::new(SgxParseCallbacks::default()))
+        .clang_args(env_c_flags())
         .clang_arg(&format!("-I{}", include_path));
 
     cargo_emit::rerun_if_changed!(include_path);
 
     builder
 }
 
+// Gets the `CFLAGS` from the environment, if any.  When there are no `CLFAGS`
+// will return an empty vector.
+// The `CFLAGS` will be split on whitespace in order to allow for multiple
+// arguments. This does *not* attempt to handle escaped shell characters,
+// https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
+fn env_c_flags() -> Vec<String> {
+    let env_flags = env::var("CFLAGS").ok();
+    env_flags.map_or_else(
+        Vec::new,
+        |flags| {
+            flags
+                .split_whitespace()
+                .into_iter()
+                .map(String::from)
+                .collect::<Vec<_>>()
+        },
+    )
+}
+
 /// SGXParseCallbacks to be used with [bindgen::Builder::parse_callbacks]
 ///
 /// This provides a default implementation for most of the SGX libraries

core/types/Cargo.toml

@@ -26,6 +26,11 @@ mc-sgx-util = { path = "../../util", version = "=0.3.1-beta.0" }
 rand_core = { version = "0.6.4", default-features = false }
 serde = { version = "1.0.145", default-features = false, features = ["derive"], optional = true }
 
+# `getrandom` is pulled in by `rand_core` we only need to access it directly when registering a custom spng,
+# `register_custom_getrandom`, which only happens for target_os = none
+[target.'cfg(target_os = "none")'.dependencies]
+getrandom = { version = "0.2", default-features = false, features = ["custom"] }
+
 [dev-dependencies]
 rand = "0.8.5"
 yare = "1.0.1"

core/types/src/error.rs

@@ -2,7 +2,6 @@
 
 //! SGX Error types
 
-use core::result::Result as CoreResult;
 use mc_sgx_core_sys_types::sgx_status_t;
 use mc_sgx_util::{ResultFrom, ResultInto};
 
@@ -22,9 +21,6 @@ pub enum FfiError {
     UnknownEnumValue(i64),
 }
 
-/// A convenience type alias for a `Result` which contains an [`Error`].
-pub type Result<T> = CoreResult<T, Error>;
-
 /// A enumeration of SGX errors.
 ///
 /// Those listed here are the ones which are identified in the `sgx_status_t`
@@ -242,7 +238,7 @@ pub enum Error {
 impl TryFrom<sgx_status_t> for Error {
     type Error = ();
 
-    fn try_from(src: sgx_status_t) -> CoreResult<Error, ()> {
+    fn try_from(src: sgx_status_t) -> Result<Error, ()> {
         match src {
             sgx_status_t::SGX_SUCCESS => Err(()),
 

core/types/src/lib.rs

@@ -23,11 +23,27 @@ pub use crate::{
     attestation_key::{AttestationKeyId, ExtendedAttestationKeyId},
     attributes::{Attributes, MiscellaneousAttribute, MiscellaneousSelect},
     config_id::ConfigId,
-    error::{Error, FfiError, Result},
+    error::{Error, FfiError},
     key_request::{KeyName, KeyPolicy, KeyRequest, KeyRequestBuilder},
     measurement::{Measurement, MrEnclave, MrSigner},
     quote::QuoteNonce,
     report::{Report, ReportBody, ReportData},
     svn::{ConfigSvn, CpuSvn, IsvSvn},
     target_info::TargetInfo,
 };
+
+// For targets that don't have a random number source we force it to always
+// fail.
+// Per https://docs.rs/getrandom/latest/getrandom/macro.register_custom_getrandom.html
+// this function will *only* be used if getrandom doesn't know of a native
+// secure spng
+#[cfg(target_os = "none")]
+use getrandom::register_custom_getrandom;
+
+#[cfg(target_os = "none")]
+register_custom_getrandom!(always_fail);
+
+#[cfg(target_os = "none")]
+fn always_fail(_buf: &mut [u8]) -> Result<(), getrandom::Error> {
+    Err(getrandom::Error::UNSUPPORTED)
+}

tservice/src/report.rs

@@ -3,9 +3,11 @@
 
 use core::ptr;
 use mc_sgx_core_sys_types::sgx_report_t;
-use mc_sgx_core_types::{ReportData, Result, TargetInfo};
+use mc_sgx_core_types::{ReportData, TargetInfo};
 use mc_sgx_util::ResultInto;
 
+pub type Result<T> = ::core::result::Result<T, mc_sgx_core_types::Error>;
+
 /// Report operations that can be performed inside of an enclave
 pub trait Report: Sized {
     /// Creates a report for the current enclave.

urts/sys/types/src/lib.rs

@@ -1,6 +1,7 @@
 // Copyright (c) 2022 The MobileCoin Foundation
 
 #![doc = include_str!("../README.md")]
+#![no_std]
 #![allow(non_camel_case_types, non_snake_case, non_upper_case_globals)]
 
 use mc_sgx_core_sys_types::{